Help! No Start: '88 GM 2.8L MPI V-6
Shannen Durphey
shannen at mcn.net
Wed Oct 15 04:40:03 GMT 1997
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Ferrill, Jess B wrote:
> I hope I am not misusing the DIY_ EFI with a mundane service problem on
> a totally stock car, but it's got me stumped :<(. Thanks for your
> patience and help.
>
> My daughter's 1988 Oldsmobile Cutlass Supreme 2 dr.(same as Chev Lumina,
> Buick Regal, Pontiac Gran Prix) with 2.8 L V-6 Multi-Port Injection
> (Auto Trans & FrtWD) would not start after sitting several days.
> Battery was low ("click, click" she said describing solenoid sound).
> Engine would still not fire after attempting jump start and re-charging
> battery. Fuel pump, filter and system was priming and ok; see 40 psi at
> the fuel rail, pressure regulator works ok dropping 5 - 10 psi when
> vacuum is applied. Spark is good and healthy, jumps 0.100" gap easily
> and regularly. Car ran well before no start problem, except for
> occasional stall when first started from cold, has 109K miles.
>
> <snipped>
>
>
>
> (P4 ECM #1227727
Hmmmm. Same ECM as 86-92 pickups. Never knew that.
>
> <more snip>
>
> Summary: After sitting with low battery and jump start/recharge,
> injectors are not getting pulsed, 12 volts is present to injectors, ECM
> has been replaced. Car will run briefly if injectors are operated with
> separate 12 volts. There may be a problem with sensor grounds.
>
> My questions for the group:
>
> 1) Any ideas?
Make sure you've got a reference pulse from the ign. module. (I see many
other suggestions about this. It's a common failure to me.) And, if TPS is
more than 2.5V at crank, ECM will go into "clear flood" mode and reduce or
remove injector pulses.
My best advice is this: if possible get your hands on a scan tool. You
need to know for certain that the ECM is getting reference pulses. Watch
"cranking rpm" if available, or "rpm" otherwise. If you can't get a scan
tool(I realize it may not be possible), you can "simulate" a ref. pulse.
With key on, injector test lamp installed, 6 way connector at ignition
module disconnected, momentarily touch ppl/white wire (circuit 430) with a
test light to 12V+. If injector fires, module is probably bad. If not,
still could be an open in circuit#430.
> 2) When a GM P4 ECM car will not run, can the ECM set any trouble
> codes? (I tried turning on ignition for 15 seconds and cranking for 15
> seconds more which was supposed to set codes on some early GM ECMs, but
> still get only "12"s).
Some ECM #'s won't set codes until the engine is running. Sensor codes that
is.
>
>
> 3) What are the minimum sensor inputs required to the ECM to make it
> provide the ground pulses for the injectors? Reference pulse from ign.
> module, crank signal, key on power, and TPS<2.5V. Check this one. Also,
> ECM will pulse injectors with other sensors unhooked, but engine probably
> won't start. Too rich.
>
> 4) Can the MEM-CAL (which was not replaced, only transferred from the
> old ECM) cause this problem and still have the ECM show "12" codes?
Usually this returns code 51 or 52 with or wothout 12.
>
>
> 5) The question as to whether C5/C10 should be grounded to the engine
> is still unanswered and is where I am concentrating my efforts. If the
> analog type EGR doesn't get a ground for its pintle position sensor will
> this prevent the injectors from being fired? If the C5/C10 sensor
> ground is not grounded to the engine will this prevent the injectors
> from firing? (I don't want to just ground C5/C10 and try it until I am
> sure that this is not supposed to be a floating or instrument ground).
> I don't want to spend too much time in this area if it can't cause
> problem.
>
Service manual shows this grounds within ECM, not to the engine.
> Thanks everyone for your help, I will post the solution when I find it.
>
> Britt Ferrill
> bferrill at amp.com
> 910+727-5387
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<HTML>
<P>Ferrill, Jess B wrote:
<BLOCKQUOTE TYPE=CITE>I hope I am not misusing the DIY_ EFI with a mundane
service problem on
<BR>a totally stock car, but it's got me stumped :<(. Thanks for
your
<BR>patience and help.
<P>My daughter's 1988 Oldsmobile Cutlass Supreme 2 dr.(same as Chev Lumina,
<BR>Buick Regal, Pontiac Gran Prix) with 2.8 L V-6 Multi-Port Injection
<BR>(Auto Trans & FrtWD) would not start after sitting several days.
<BR>Battery was low ("click, click" she said describing solenoid sound).
<BR>Engine would still not fire after attempting jump start and re-charging
<BR>battery. Fuel pump, filter and system was priming and ok; see
40 psi at
<BR>the fuel rail, pressure regulator works ok dropping 5 - 10 psi when
<BR>vacuum is applied. Spark is good and healthy, jumps 0.100" gap
easily
<BR>and regularly. Car ran well before no start problem, except for
<BR>occasional stall when first started from cold, has 109K miles.
<P><snipped></BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE> </BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE>
<BR> </BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE> (P4 ECM #1227727</BLOCKQUOTE>
Hmmmm. Same ECM as 86-92 pickups. Never knew that.
<BLOCKQUOTE TYPE=CITE> </BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE><more snip>
<BR> </BLOCKQUOTE>
<BLOCKQUOTE TYPE=CITE>Summary: After sitting with low battery and
jump start/recharge,
<BR>injectors are not getting pulsed, 12 volts is present to injectors,
ECM
<BR>has been replaced. Car will run briefly if injectors are operated
with
<BR>separate 12 volts. There may be a problem with sensor grounds.
<P>My questions for the group:
<P>1) Any ideas?</BLOCKQUOTE>
Make sure you've got a reference pulse from the ign. module. (I see many
other suggestions about this. It's a common failure to me.) And,
if TPS is more than 2.5V at crank, ECM will go into "clear flood" mode
and reduce or remove injector pulses.
<P>My best advice is this: if possible get your hands on a scan tool.
You need to know for certain that the ECM is getting reference pulses.
Watch "cranking rpm" if available, or "rpm" otherwise. If you can't
get a scan tool(I realize it may not be possible), you can "simulate" a
ref. pulse. With key on, injector test lamp installed, 6 way connector
at ignition module disconnected, momentarily touch ppl/white wire (circuit
430) with a test light to 12V+. If injector fires, module is probably
bad. If not, still could be an open in circuit#430.
<BLOCKQUOTE TYPE=CITE>
<P>2) When a GM P4 ECM car will not run, can the ECM set any trouble
<BR>codes? (I tried turning on ignition for 15 seconds and cranking
for 15
<BR>seconds more which was supposed to set codes on some early GM ECMs,
but
<BR>still get only "12"s).</BLOCKQUOTE>
Some ECM #'s won't set codes until the engine is running. Sensor
codes that is.
<BLOCKQUOTE TYPE=CITE>
<P>3) What are the minimum sensor inputs required to the ECM
to make it
<BR>provide the ground pulses for the injectors? Reference pulse
from ign. module, crank signal, key on power, and TPS<2.5V. <I>
Check this one. </I> Also, ECM will pulse injectors with other sensors
unhooked, but engine probably won't start. Too rich.
<P>4) Can the MEM-CAL (which was not replaced, only transferred from
the
<BR>old ECM) cause this problem and still have the ECM show "12" codes?</BLOCKQUOTE>
Usually this returns code 51 or 52 with or wothout 12.
<BLOCKQUOTE TYPE=CITE>
<P>5) The question as to whether C5/C10 should be grounded
to the engine
<BR>is still unanswered and is where I am concentrating my efforts.
If the
<BR>analog type EGR doesn't get a ground for its pintle position sensor
will
<BR>this prevent the injectors from being fired? If the C5/C10 sensor
<BR>ground is not grounded to the engine will this prevent the injectors
<BR>from firing? (I don't want to just ground C5/C10 and try it until
I am
<BR>sure that this is not supposed to be a floating or instrument ground).
<BR>I don't want to spend too much time in this area if it can't cause
<BR>problem.
<BR> </BLOCKQUOTE>
Service manual shows this grounds within ECM, not to the engine.
<BLOCKQUOTE TYPE=CITE>
<P>Thanks everyone for your help, I will post the solution when I
find it.
<P>Britt Ferrill
<BR>bferrill at amp.com
<BR>910+727-5387</BLOCKQUOTE>
</HTML>
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